Integrate first SQL Notebooks Bits into Master (#3679)

* First crack tsql notebook (no output rendered yet)

* getting messages back

* intellisense working first cell, no connection errors

* sql notebook cell output functioning

* Latest SQL noteobook changes

* Undo change to launch.json

* Plumbing providers through

* Kernels shown from multiple providers, can switch between them. No mementos yet

* Ensure we have a feature flag for SQL notebooks, ensure existing functionality still works

* Fix tslint duplicate imports issue

* Addressing PR comments

* second round of PR feedback to cleanup notebook service manager code

* merge latest from master

src/sql/services/notebook/sessionManager.ts

@@ -1,3 +1,7 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
 'use strict';
 
 import { nb } from 'sqlops';